High energy costs and continuing emphasis on the conservation of irreplaceable energy sources such as petroleum have spurred many efforts to develop viable alternatives to conventional internal combustion engines of the reciprocating and rotary types. One avenue which has been explored is the development of indirectly fired gas turbine engines. In these the gas or liquid fuel fired, internal combustor conventionally employed to produce hot gases to drive a turbine is replaced by an external heat source. This may be an external combustor operated on an alternative fuel such as coal or a renewable fuel such as wood-waste products, or the heat may be recovered from an industrial or other process in circumstances in which it would otherwise be wasted.
In any case, the hot gases available from the external heat source are circulated through an appropriate heat exchanger in heat transfer relationship to air discharged from the compressor of the gas turbine engine. This heats the air which is then circulated to the turbine of the engine to drive the latter.
A number of indirectly fired gas turbine engines have heretofore been suggested as shown by U.S. Pat. Nos. 2,677,236 issued May 4, 1954, to Grinstad; 3,321,930 issued May 30, 1967, to LaFleur; 3,864,919 issued Feb. 11, 1975, to Frutschi; 3,868,818 issued Mar. 4, 1975 to Itoh; and 3,932,996 issued Jan. 20, 1976, to Bammert et al.